Toothbrushes



Jan. 15, 1963 R. G, CLAYTON ETAL 3,072,944

TOOTHBRUSHES Filed Jan. 21, 1960 koazkr a. CLAYTON ztw s u. HALBERSTADT BENJAMIN TAR/N BY cw 2w:

A TTORNE rs United States Patent 3,072,944 TOOTHBRUSHES Robert G. C layton, Southampton, and Lewis J. Halberstadt, W1llramsburg, Mass, and Benjamin Tarin, Philadelplua, Pa., assignors to Pro-Phy-Lac-Tic Brush Company, Florence, Mass, a corporation of Delaware Filed Jan. 21, 1960, Ser. No. 3,843 6 Claims. (Cl. 15-167) This invention relates to toothbrushes of the type which combines groups of bristle-tufts of different degrees of stiffness.

Various such arrangements have been proposed in an effort to improve the combined cleansing and massage qualities of the brush. Such proposals insofar as they have met with success have been dependent in substantial measure on a degree of acquired skill in their use. Further, a wide variety of individual preferences exist based on comfort and individual brushing habits and practice, resulting from variation in the individuals oral and dental structure and intangibles.

While for some individuals there is a preference both from the personal and objective point of view for a brush having predominantly stiff or soft bristles, the general advantages of the type which properly combines bristle-tufts of different degrees of stiffness ,is professionally established. However, personal prejudices in favor of a stiff or soft bristle have militated against a general public acceptance of those brushes which seem, in use too stiff or too soft to the user prejudiced in either direction.

Synthetic bristle material such as nylon, has, because of its greater durability, uniformity, and availability, increasingly supplanted natural brisles. In using synthetic bristle material the capacityof the brush block to hold water is in substantial degree sacrificed since, as later pointed out, the synthetic bristle is substantially non-absorptive and because of its smooth surface characteristics water readily drains from the brush.

One object of the present invention is to provide a toothbrush construction which provides in substantial measure the cleaning and massage characteristic of the hard-soft brush, which the dental profession seems to have found desirable, in a manner to meet professional approval and which at the same time bridges some personal prejudices with respect to an overall stiff orsoft feel in use.

A further object is to provide a brush having an improved mode of operation as the brushing progresses from the scrubbing phase .to massage, or where these two phases are intermingled, overlapped, or even reversed v by individual users. v

A further object is to provide a toothbrush construction which while closely approximating an all synthetic bristle brush in durability at the same time provides a brush block having water and moisture holding character and capacity sufficient to secure in adequate degree the functional advantages which such characteristics afford.

Other and further objects and advantages will be made apparent in the following specification and claims.

It has been found that in large measure the ffeel of a toothbrush in use is dependent on its water absorptive properties and the ability of the bristle block as a whole to retain water. The water absorptive properties of natural and synthetic bristles are quite different. If plotted on a graph with water absorption as the horizontal scale and stiffness as the vertical scale, the curve for natural bristles will be a long, gentle sloping substantially straight line with an eventual water absorption of 10% to 30% If synthetic bristle (nylon for-example) is plotted on this same graph its curve will drop very 3,072,944 Patented Jan. 15, 1963 mum water absorption of 2%, and maximum softness, and then continue in a level line from that point on.

Natural and synthetic bristles also undergo further physical change in use, the ends of the natural bristles which start off sharp and ragged wear down into a rounded blunt form, and also tend to split or fiag on the ends. Synthetic bristles start out with flat ends, relatively sharp at the edges, also wear to a blunt rounded end but without splitting or fiaging.

The present invention takes advantage of the initial stiffness of natural bristles and its water absorptive prop erties with an accompanying decrease in stiffness, to provide novel features of operation and brush construction.

As above pointed out the eventual water absorption of natural bristle varies over a substantial range. Natural bristle, like all natural products vary in physical prop erties. As later more specifically pointed out, it has been found that by using suitable blends of natural bristles, a general initial degree of stiffness with a degree of subsequent softening under water absorption can be secured which when used in combination with synthetic bristles of known stiffness and substantially negligible water absorption in accordance with the teaching of the invention, provide a toothbrush whichfunctions in a professionally satisfactory manner in regard to cleaning and massage and finds personal acceptance by a range of users whose preferences lie in the area between the ex} tremes of hardness and softness.

In the accompanying drawing:

FIG. 1 is a side elevational view of a tooth trating one embodiment of the invention;

FIG. 2 is aplan view of the brush of FIG. 1;

FIG. 3 is a side elevational view of a toothbrush illustratively embodying an alternative form of the invention; and v FIG. 4 is a side elevational view of the brush of FIG. 3.

Referring to. FIGS. 1 and 2 of the drawing the brush is shown as comprising a brush block, generally indicated at 1, comprising two center rows 2 of bristle tufts formed rush illusnatural bristle material, and outer rows 3 of synthetic bristle, such as nylon. The bristle-tufts of both sets are secured to a handled-back 4 in any suitable or conven tional manner as by stapling the tufts in spaced openmgs provided in the back. I

In the brush illustrated in FIGS. 1 and 2 the tufts making up the center rows 2 are formed from natural bristle while the outer rows 3 are made of synthetic bristles, such as nylon. V

The natural bristles of rows 2 are relatively stiff when dry while the synthetic bristles of row 3 are made sufficiently fine so thatthey are relatively soft, that 1s more easily flexed, than the natural bristles. For the purposes of the invention black natural bristles have been found preferable to white bleached natural superior to some perior.

bristle. Washing, scouring, and bleaching all tend to degrade the quality of the bristle. In general the less processing the bristle is given the better the bristle for the purposes of the invention. Bristle is a protein material made up of amino acids, an important one of which is cystine. Whenthe bristle is bleached, the disulphide bond of the cystine is broken. Since wearing qualities seem to be tied in with the disulphide bond it is presumed that bleaching lowers the wearing qualities and embritties the bristle by taking out the natural oils and fats. This does not mean, of course, that a carefully processed 'high grade bleached white bristle could not be poor grade of unbleached black bristle, but grade for grade the unbleached black bristle is sua For the purposes of the invention and considering presently available supplies of natural bristle a blend consisting of 25% long black India bristle and 75% long black Chungking bristle has been found satisfactory. These bristle lengths are out into appropriate length for stapling. It will be understood that in the'stapling each bristle length forms two free ends in the bristle block. Since, the object of blending the two named sources of bristles is to secure the correct stiffness and optimum wear in the natural bristle tufts, the percentages in the blend may be varied using natural bristles from different sources or to meet variation in bristle characteristics which may occur in successive shipments. The generally preferable flexibility characteristics of the synthetic bristles making up the tufts of rows 3 as compared with the natural bristle blend above described in the rows 2, is obtained by using nylon bristles having a diameter of .009 of an inch. It will be understood that the size of the nylon bristles may be variedeither way as may be found desirable to complement the characteristics of the available natural bristles in order to secure the desired function of the brush block as a whole. Further, the degree of differential can be controlled by selection of synthetic bristles of appropriate size to achieve desired functional characteristics in the brush.

, In the initial use of the brush the portion of the brush block made up ofthe natural bristles are. at maximum stiffness and provide the stiffnessrequisite for adequate cleaning. As the natural bristles absorb moisture from the dentifrice used or from an initial wetting of the'brush with water and from oral moisture, the natural bristles tend to soften. This does not mean that the maximum water absorption should or does immediately take place, the natural bristles retain adequate stiffness for a length of time at least adequate for cleaning purposes, but a decrease in the stiffness dfferential between the natural and synthetic bristles occurs. In the meantime and from the start ofthe brushing operation, the presence of the soft synthetic bristles of the rows 3 have modified the ffeel of the brush, block as a Whole and in the final massage strokes of the brushing operation the overall softness of the brush increases as the, moisture-softened stiff natural bristles. more, nearly approach the softness of the synthetic bristles. Aside from the'water absorption the brush block, as a whole, retainsa larger quantity of water due lto the greater moisture retaining properties ,of the surface characteristics of the natural bristles'as compared to the smooth surfaceof synthetic bristles.

' As a result many users prejudiced in favor of the feel of stiff natural bristles, and consciously or unconsciously accustomed to the. increasing softnessof the, brush block due to water absorption may findthe compositeb-rush acceptable and at'the same time secure the professionally recognized advantage of the softer synthetic bristles duringthe overall, brushing operation. Similarly, the user prejudiced in favor 'o-fthe feet of softer bristles, "'while perhaps momentarily disturbed by the initial stiffness of thernatural bristles-winds up the brushing operation with a brush more nearly approximating the feel of an overall soft, brush than is the'case with the presently available all synthetic composite bristle brushes.

Natural bristle, particularly in its dry state is relatively brittle, a tendency which because of breakage shortens the useful life of natural bristle brushes in comparison withthe, more resilient synthetic bristle material. As natural bristle softens from the absorption of water its loss of stiffness is accompanied with a loss of resilience resulting in permanent distortion which further shortens the useful life of natural bristle brushes in comparison with brushesmade with synthetic bristle material which retains its resilience when moist.

In the arrangement of FIGS. 1 and 2 the .softer syntheticbristles of the outer rows. oftufts flex into and intermingle with adjacent nat- "tiral bristles'of the adjacent inner row giving advantageous support to the natural bristles until their brittlenessFan-d block 6 are made up of synthetic bristles while the tufts of the outer rows 7 are made up of natural bristles.

While the stiffness of the tufts formed of natural bristles may to some degree be varied by blending, the stiffness differential of the rows of tufts is easily varied by increasing or decreasing the size (cross-sectional diameter) of the synthetic bristles used.

Thus, having reference to FIGS. 3 and 4, if synthetic bristles of a size to provide a stiffness substantially equal to that of the natural bristle making up the tufts of rows 7, when the latter are in a dry state, are used to make up the tufts of the rows 5, the brush starts operation as an overall stiff brush, but as the brushing operation continues the Water absorption of the natural bristles introduces a stiffness differential between the inner and outer rows of bristles, as the natural bristles of the outer rows soften while the synthetic bristles of the inner row retain substantially their original stiffness. The degree of the differential attained can, as in the arrangement of FIGS. 1 and 2, be varied by selection of synthetic bristles of appropriate stiffness for the inner rows. In any case the initial differential might, if desired, be made substantially equal to the degree of softening which the natural bristles undergo from moisture absorption so that the brushing operation starts with a stiffness appropriate to cleaning but ends up with an overall softness appropriate for massage purposes. The latter combination is advantageous for those users who tend to employ a concentrated or overly vigorous gum massage at the end of the cleaning operation.

The versatility in brush operation obtained by the broad concept of using in a composite brush structure two bristle materials having varying degrees of water absorption is apparent.

In whatever way the synthetic and natural bristles are combined and whatever bristle or tuft pattern used, in additionto the specific advantages a given pattern may provide, the presence of the natural bristles increases the yvater holding capacity of the brush block with its attend-- ant advantages at the same time that the overall durability bristles are preferred because of their known brushingqualities and their availability it will be understood that other materials suitable for toothbrush use and having appropriately different water absorptive properties resulting in a varying stiffness diiferentital may be used in practicingthe invention and that the tuft pattern, num-- her and size of the tufts may be varied as found necessary in providing brushes for adult, child, or juvenile use, or for special purposes.

Although the invention has perhaps its greatest utility in toothbrushes of the type illustrated which combine hard and soft bristles in a manner to satisfy cleaning and massaging requirements, it will be understood that it is also applicable to other types of toothbrushes heretofore formed entirely of natural or entirely of synthetic bristles where the functional relationships above disclosed have advantage.

What'is claimed is:

, l. A toothbrush comprising a brush block consisting entirely of apluralityof spaced bristle tufts, each tuft consisting of a'multiplicity of contiguous bristle elements,

one portion of the tufts being made up entirely of bristle having negligible moisture absorptive properties and characterized by a constant flexibility, a second portion of the tufts being made up entirely of relatively stifl bristle elements having moisture absorptive properties and characterized by an increase in flexibility upon absorption of moisture during the cleaning portion of a brushing cycle to approximately the flexibility of the bristle elements of said one portion, whereby the overall stiffness of the bristle elements of the brush block at the end of the cleaning portion of a brushing cycle approximates that of the elements of said one portion.

2. A toothbrush comprising a brush block consisting entirely of a plurality of spaced bristle tufts, each tuft consisting of a multiplicity of contiguous bristle elements, arranged in at least three extending rows, the bristle elements in the tufts making up the inner, and those making up the outer rows, diflering in stiffness when dry, the more flexible bristle elements being formed of a material having negligible moisture absorption properties and characterized by a constant flexibility, the stifier bristle elements being formed of a material having relatively high moisture absorption properties and characterized by an increase in flexibility upon absorption of moisture during the cleaning portion of a brushing cycle to approximately the flexibility of the said more flexible bristle elements, whereby the overall stiflness of the bristle elements of the brush block, at the end of the cleaning portion of a brushing cycle approximates that of said elements having negligible Water absorptive properties.

3. A toothbrush as in claim 2 the said stiffer bristle 6 elements being natural bristle and the said more flexible bristle elements being formed of synthetic plastic material.

4. A toothbrush as in claim 2, the said stifier bristle elements being unbleached natural bristle and said more flexible bristle elements being formed of synthetic plastic material.

5. A toothbrush as in claim 2, the said stiffer bristle elements being a blend of substantially 25% unbleached black, natural India bristle and unbleached black, natural Chungking bristle, and the said more flexible elements being formed of nylon.

6. A toothbrush as in claim 2, the said stiffer bristle elements being located in the inner of the rows of tufts.

References Cited in the file of this patent UNITED STATES PATENTS 1,022,920 Anderson Apr. 9, 1912 1,251,250 Libby Dec. 25, 1917 1,953,980 Teller Apr. 10, 1934 2,396,548 Allen Mar. 12, 1946 2,845,649 Hutson Apr. 5, 1958 2,876,477 Stewart Mar. 10, 1959 FOREIGN PATENTS 557,790 France May 19, 1923 618,049 France Mar. 2, 1927 642,910 France Sept. 6, 1928 826,440 Germany Jan. 2, 1952 1,203,916 France Aug. 3, 1959 

1. A TOOTHBRUSH COMPRISING A BRUSH BLOCK CONSISTING ENTIRELY OF A PLURALITY OF SPACED BRISTLE TUFTS, EACH TUFT CONSISTING OF A MULTIPLICITY OF CONTIGUOUS BRISTLE ELEMENTS, ONE PORTION OF THE TUFTS BEING MADE UP ENTIRELY OF BRISTLE HAVING NEGLIGIBLE MOISTURE ABSORPTIVE PROPERTIES AND CHARACTERIZED BY A CONSTANT FLEXIBILITY, A SECOND PORTION OF THE TUFTS BEING MADE UP ENTIRELY OF RELATIVELY STIFF BRISTLE ELEMENTS HAVING MOISTURE ABSORPTIVE PROPERTIES AND CHARACTERIZED BY AN INCREASE IN FLEXIBILITY UPON ABSORPTION OF MOISTURE DURING THE CLEANING PORTION OF A BRUSHING CYCLE TO APPROXIMATELY THE FLEXIBILITY OF THE BRISTLE ELEMENTS OF SAID ONE PORTION, WHEREBY THE OVERALL STIFFNESS OF THE BRISTLE ELEMENTS OF THE BRUSH BLOCK AT THE END OF THE CLEANING PORTION OF A BRUSHING CYCLE APPROXIMATES THAT OF THE ELEMENTS OF SAID ONE PORTION. 